<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .main{
            width:10px;

            border:5px solid gray;
            margin:0px;
            background-color: #79d27f;
        }

    </style>
</head>
<body>
<div class="main">

</div>
</body>
</html>